Does "spinning the ball in" increase your shooting margin of error?

[Patrick Johnson]

Think my last post was off the point a little. I wasn't talking there about decreasing the margin for error, but just saying that I didn't think such small amounts of english increased it significantly.

A better example might be: let's say you're hill-hill, $100 or some other meaningful amount of money on the line ... you're shooting a moderate cut on the 9 (less than half-table), it's by the short rail and 2 diamonds from the pocket. If it's a half-inch off the rail, how do you cinch it? And what if it's frozen? Do you still like center ball?

Even more. The reasons that center ball is more reliable don't change because you're on the 9 or you've got money on the game - center ball becomes more important because of those things.

You have to hit the right OB contact point with spin just like you have to without spin. That point doesn't get any bigger because you've added spin; it just gets a little harder to figure exactly where it is (its location moves with more or less spin) and a little harder to hit it (because of squirt/swerve). Why make the shot harder?

pj
chgo

 

[JoeyInCali]

And what if it's frozen? Do you still like center ball?
I'd put a little inside english on it.

 

[Patrick Johnson]

And what if it's frozen? Do you still like center ball?
I'd put a little inside english on it.

Depends on the angle. You can come up with a few specific situations where some spin might help, but that doesn't change the general principle.

pj
chgo

 

[Travis Bickle]

I'm with Joey. I'll hit the frozen shot at about 1 o'clock. If off the rail, I'd like 11:30 to 11:45 ...

 

[Jal]

Yes. The reasons that center ball is more reliable don't change because you're on the 9.

You have to hit the right OB contact point with spin just like you have to without spin. That point doesn't get any bigger because you've added spin; it just gets a little harder to figure exactly where it is (its location moves with more or less spin) and a little harder to hit it (because of squirt/swerve). Why make the shot harder?

pj
chgo

Agreed again. Look at the first plot on page 17 of Dr. Dave's article here:

http://billiards.colostate.edu/technical_proofs/new/TP_A-28.pdf

This is for a fully rolling cueball (PEr=100%) with zero sidespin (PEe=0%). (The subcripts r and e are covered a bit by those green squiggles.)

The blue curve represents a very moderate cueball speed of 3.4 mph. It shows very little throw, only up to about 1 degree through cut angles ranging from 0 to 45 degrees. Faster speeds produce even less throw (green line for instance)

More important are the plots which show how much the throw varies if you change the amount of english, intentionally or unintentionally. The last one on page 6 and first one on page 7 show this for a fully rolling cueball at cut angles of 30 and 60 degrees, respectively. With zero english, the curves are relatively flat, meaning the amount of throw is not very sensitive to tip placement.

At the same time, these same plots show that the slopes of the curves begin to increase as you employ outside english (move to the right in the diagrams). While you are reducing throw to be sure, you're paying a dear price: you're getting a considerably increased sensitivity of throw to the amount of english used, thereby making the throw angle and the overall cut angle harder to predict. And for this you're adding the complications of squirt and swerve?

They also show that inside english (on the left half of the diagrams) is even better than no english at flattening out the curves. But as with outside, you now have to deal with the two S's.

Just rolling the cueball seems to be the pretty clear winner if your goal is to cinch a shot, position be damned.

Jim

 

[jsp]

Jsp, I don't think there is any real advantage when you factor in the added complications of squirt and swerve.

Hitting thicker does reduce the "geometric" margin of error, but not that much. Throw compensation is pretty small as well. The greatest "automatic" correction to a cut angle error that throw provides is when the balls end up rolling across each other on a stun shot. Here you get the most variation in throw with variations in surface speed. For some cut angle A and english spin Wz, where V is the cueball's speed and R its radius, the relative surface speed between the cueball and object ball on a stun shot is:

Vs = Vsin(A) - RWz

If this surface speed isn't too great, the balls end up rolling during impact. In this case, 1/7'th of this surface speed becomes the sideways throw velocity of the object ball. Since the object ball's forward speed is Vcos(A), the throw angle T is:

T = Atan[(1/7)(Vsin(A)-RWz)/Vcos(A)] = Atan[(1/7)(sin(A)-RWz/V)/cos(A)]

For simplicity, let's assume that RWz/V=sin(A), so that the surface speed and throw would be zero if we actually cut the ball at angle A. But instead, we cut it at angle A' (keeping RWz the same). Now we have a throw angle T', and the difference is:

T' - T = T' - 0 = Atan[(1/7)(sin(A')-sin(A))/cos(A')]

So if we overcut what should have been a 30 degree cut by 4 degrees, the throw compensation would be:

T' - T = T' - 0 = Atan[(1/7)(sin(34)-sin(30))/cos(34)] = 0.58 degree

The correction is about 1/7'th of the cut angle error. Well it is something, but is it worth the squirt and swerve stuff? And you get even less correction if the cueball has draw or follow on it or the spin/speed ratio RWz/V is not very close to sin(A). Since that cosine in the denominator gets very small as you approach 90 degree cuts, it may seem like there might be a real advantage there. But the unfortunate fact is that you have to get the spin/speed ratio RWz/V closer and closer to sin(A) to get the balls to roll across each other. (I know you're not actually prescribing getting the ratio very close, but it gives us an idea of what the maximum correction can be.)

Interesting idea though, and maybe it bears further thought.

Jim

Jal, once again, you're the man when it comes to such discussions. But you did just show that there is a degree of correction that takes place when you spin balls in, which is what I was looking for.

But of course, the practical question is if that slight increase in margin of error is worth it you introduce all that squirt and swerve? Most likely not, but I still find myself subconsciously doing it on certain shots. Maybe it's just wrong, but I also notice many professionals do it on some shots as well.

But as I think about it more, the shots where I do spin balls in are shots where I fear that naturally roll the CB would put a scratch into play. If there is no way I would scratch, I would almost always use natural roll on cut shots (to cinch shots, neglecting position play) to minimize throw. But there are certain shots where scratching is a concern using natural roll, so I hit the CB with stun. But I know that stunning the CB without english maximizes throw, so I believe I subconsciously overcompensate by applying outside english, more than enough to compensate for throw.

 

[jsp]

You have to hit the right OB contact point with spin just like you have to without spin. That point doesn't get any bigger because you've added spin...

But it can get bigger, provided you add the right amount of outside spin for a particular cut shot angle.

Take a look at the graph below from Dr. Dave's article that Jal has linked. The plot shows the amount of throw (y-axis, measured in degrees) versus cut angle (x-axis, measured in degrees) for a stun hit (PEr=0%) and a fair amount of outside english (PEe=75%). The red, blue, and green lines represent soft, medium, and firm shots, respectively.

The thing to note is where these lines cross the zero point on the y axis, which seems to be about 70 degrees. This indicates that for a 70-degree cut shot and for that particular amount of outside english (75% of "maximum"), then you would perfectly compensate for any CIT, and that the balls would roll across each other at the contact point, giving you absolutely zero throw. To the left of this point, the curve is negative, which indicates you're actually throwing the ball due to the overspin. To the right of this point, the curve is positive, which is the "bad" type of throw.

The thing to notice is the slope of the lines to the left of the zero crossing point. Just looking at the medium-hit shot (blue line), between approximately a 32-degree cut and a 65-degree cut, the slope of the line is positive. This indicates the amount of "automatic correction" (Jal, I like that term) for that particular amount of outside english. The slope is about 1/7, which lines up with Jal's calculation...meaning that for every degree of cut angle error, the outside english compensates 1/7th of that amount.

In the ideal, zero-friction case, then the slope of the lines would all be zero, meaning no automatic correction. Any positive slope on the graph is "good", meaning there is auto correction (positive slope and negative throw would be the best combination). Any negative slope would be "bad", which means the more cut angle error you have, the throw error (or lack of throw) will add to the error, making the contact point even smaller than the zero-friction case (negative slope and positive throw would be the worst combination).

So it is true that the OB contact point in which you can pocket a shot can get bigger depending on the amount of english and the cut angle.

...it just gets a little harder to figure exactly where it is (its location moves with more or less spin) and a little harder to hit it (because of squirt/swerve). Why make the shot harder?

But of course, this is true as well. Not only do you introduce squirt and swerve into the picture, but the precise amount of outside spin is also another variable to control. From the first set of graphs on Dr. Dave's link, it shows how much the throw can change for a small amount change in english. The amount of throw can change a whole 2 degrees for only a 10% change in outside english. With all those variables coming into the picture, it surely does not seem it is all worth the small increase in contact point.

BUT...if you can control the amount of serve, and the amount of squirt, and the amount of english, and you know exactly where to contact the OB given those variables, then your margin of error does get bigger for a certain amount of outside english.

EDIT: Just wanted to add that those graphs from Dr. Dave's article kick some serious butt! Thanks Dr. Dave!...and Jal for linking them. Such interesting information encoded in those few graphs, if you take the few minutes to actually decode what they mean.

EDIT2: Modified something above that was completely incorrect. I wrote it late yesterday night, so I must have been sleepy. Also, wanted to add that Jal had already described pretty much what I explained regarding the slope of the curves, but somehow yesterday I just glossed over those explanations. Should have just quoted what he wrote first, but I guess I was too excited looking at the graphs myself instead of reading what he posted regarding the graphs.

 

[Travis Bickle]

It's interesting to me the different ways people think of spinning vs. not spinning. These equations are kind of mind-bending to me. But that's just me, since my personal preference is to spin. I don't know if it's valid to say one way is higher-percentage than the other ... it may come down to how a given player sees a shot and how he feels it, too. And what kind of strokes he has developed.

Reminds me of when I was a kid taking tennis lessons. For a little while I went to a fairly respected junior academy where they had their own gold standard. And that was, since it was the mid-70s, probably the Stan Smith/Dick Stockton/Brian Gottfried way of hitting it with, you guessed it, an absence of "excess" spin. When Borg came along with his looping topspin, they told me he was a "freak" and that "he'd never win another tournament" once everybody adjusted to his style. Well, Borg did OK, and look around ... how do people play tennis now?

 

[poolstar31]

You need to perfect cutting the ball with spin and with out. Both shots have a time and place. ME? After years of leaving myself the wrong angle, I can spin pretty good. LOL

 

[Travis Bickle]

After years of leaving myself the wrong angle, I can spin pretty good. LOL

Hah, you know how I got there, too! Guess necessity might be the mother of dissension.

 

[jsp]

Maybe it's just wrong, but I also notice many professionals do it on some shots as well.

What better example of a professional than Efren? Check out the 9 balls Efren makes in the following videos...

http://www.youtube.com/watch?v=pBkuyXgjHiE (forward to 3:34)

http://www.youtube.com/watch?v=DgK5WEZDPsU (forward to 6:35)

It is clear that Efren stunned the CB with outside english, as if evident by the way the CB came off the rail after contacting the 9 ball. Efren could have easily rolled the CB in each case, but he didn't. He chose to spin the ball in.

There's gotta be some substance as to why some of the best players in the world tend to do this.

 

[JoeyInCali]

What better example of a professional than Efren? Check out the 9 balls Efren makes in the following videos...

http://www.youtube.com/watch?v=pBkuyXgjHiE (forward to 3:34)

http://www.youtube.com/watch?v=DgK5WEZDPsU (forward to 6:35)

It is clear that Efren stunned the CB with outside english, as if evident by the way the CB came off the rail after contacting the 9 ball. Efren could have easily rolled the CB in each case, but he didn't. He chose to spin the ball in.

There's gotta be some substance as to why some of the best players in the world tend to do this.

Pros never roll the 9 ball in.

 

[predator]

What better example of a professional than Efren? Check out the 9 balls Efren makes in the following videos...

http://www.youtube.com/watch?v=pBkuyXgjHiE (forward to 3:34)

http://www.youtube.com/watch?v=DgK5WEZDPsU (forward to 6:35)

It is clear that Efren stunned the CB with outside english, as if evident by the way the CB came off the rail after contacting the 9 ball. Efren could have easily rolled the CB in each case, but he didn't. He chose to spin the ball in.

There's gotta be some substance as to why some of the best players in the world tend to do this.

I think he does this to make the cueball go two rails after contact. That way he is absolutely assured against scratching and he's able to execute a little quicker, more positive stroke. Contacting two cushions after potting the final nine serves it's purpose. Maybe he didn't need it on this particular angle, but two cushion shape even after potting the final ball is a habit for most pro 9ballers. Without using two cushion shape, just rolling it and bouncing off of bottom cushion can quite often get the cueball dangerously close to the side pocket, especially if the table is very quick. I have never seen any pro lose the cueball into the pocket after potting the 9ball.

 

[hemicudas]

I think he does this to make the cueball go two rails after contact. That way he is absolutely assured against scratching and he's able to execute a little quicker, more positive stroke. Contacting two cushions after potting the final nine serves it's purpose. Maybe he didn't need it on this particular angle, but two cushion shape even after potting the final ball is a habit for most pro 9ballers. Without using two cushion shape, just rolling it and bouncing off of bottom cushion can quite often get the cueball dangerously close to the side pocket, especially if the table is very quick. I have never seen any pro lose the cueball into the pocket after potting the 9ball.

You are exactly right, Predator.

 

[hemicudas]

Pros never roll the 9 ball in.

Men, pros don't and a few women don't. Women don't draw the ball out two rails as often as they should. They just roll back one rail too frequently. POWER the ball out. Less room for error two rails.

 

[LAlouie]

Why would I tend to do this? Here's an interesting thought. Does spinning a ball in actually increase your shooting margin of error

If you don't apply english on whitey, you have to hit the ob at a certain spot to pocket it. If you DO put english on whitey, you STILL have to hit the ob in a certain spot to pocket it. Mike Segal advocates a touch of outside to compensate for throw, but even that is assuming you hit the ob in a certain spot.

I have found that I, and I notice this in many amateurs, will apply outside if I "don't trust" my aim. I think you are seeing the ball better lately, and it may or may not last because it is not the best habit to get into.

 

[Patrick Johnson]

jsp:
What better example of a professional than Efren? Check out the 9 balls Efren makes in the following videos...

http://www.youtube.com/watch?v=pBkuyXgjHiE (forward to 3:34)

http://www.youtube.com/watch?v=DgK5WEZDPsU (forward to 6:35)

It is clear that Efren stunned the CB with outside english, as if evident by the way the CB came off the rail after contacting the 9 ball. Efren could have easily rolled the CB in each case, but he didn't. He chose to spin the ball in.

I don't think that's clear in either case. It looks to me like Efren chose not to spin the CB either time. But I wouldn't say that means it's a bad idea - I don't think what one pro does on two shots is much evidence of anything.

There's gotta be some substance as to why some of the best players in the world tend to do this.

Even if it's true that some pros tend to do this (I agree with that, even if Efren didn't do it in these videos), why does that make it a good idea? Other pros don't do it. Doesn't that make it a bad idea? These "appeals to authority" are meaningless.

pj
chgo

 

[jsp]

I don't think that's clear in either case. It looks to me like Efren chose not to spin the CB either time.

How can you say this? Efren surely didn't roll the CB, as is evident from the direction the CB came off the 9 ball. So he at least hit the CB with stun. From the way the CB came off the rail, it seems as if he did apply some amount of outside.

But I wouldn't say that means it's a bad idea - I don't think what one pro does on two shots is much evidence of anything.

You're right, but I can find many other videos of professionals "cinching" the 9 by spinning it in, where they could have easily just rolled them in. But I didn't want to spend my whole night parsing youtube videos.

Even if it's true that some pros tend to do this (I agree with that, even if Efren didn't do it in these videos), why does that make it a good idea? Other pros don't do it. Doesn't that make it a bad idea? These "appeals to authority" are meaningless.

I don't think they're meaningless at all. You're right, it could be a good idea, and it also could be a bad idea. But if a couple world champions do it regularly, you really have to wonder why they do it. Theory and mathematical models/equations can only get you so far, sometimes you just have to listen to what decades worth of practical experience at the world-class level shows us. If Efren does it, and Strickland does it, and Sigel does it, and Schmidt does it, do they have any less authority on making a shot than what a physics professor at MIT says?

 

[jsp]

I think he does this to make the cueball go two rails after contact. That way he is absolutely assured against scratching and he's able to execute a little quicker, more positive stroke.

You bring up a good point. Maybe the reason he went two rails is so that he could let his stroke out, which for him would increase his overall margin of error. But he surely could have rolled the CB with a soft to medium stroke, and not be in any fear of scratching, unless he executes the shot very firmly.

Because of the fairly close proximity of the CB to the 9 ball, to achieve full roll at contact, Efren would have to hit high enough on the CB. The fact that he would have to hit the CB fairly high probably made him not want to do that, since it would have reduced his overall shooting accuracy (similar to bridging off the rail) comparing to cueing at center ball or a bit below center. Maybe that's the real reason why certain pros don't roll the 9 ball more often.

 

[Patrick Johnson]

Me:
It looks to me like Efren chose not to spin the CB either time.

jsp:
How can you say this? Efren surely didn't roll the CB, as is evident from the direction the CB came off the 9 ball. So he at least hit the CB with stun.

Yes, but that's not the kind of spin we're talking about.

From the way the CB came off the rail, it seems as if he did apply some amount of outside.

This is where I differ - it didn't look to me like any more spin than the CB would pick up from hitting the OB with stun. In other words, it looks like Efren hit the CB low/center, not low/left.

If Efren does it, and Strickland does it, and Sigel does it, and Schmidt does it, do they have any less authority on making a shot than what a physics professor at MIT says?

This is the kind of appeal to authority I'm dismissing: the kind where you name one or a few great players who may do it (how do you even know?) and ignore all the rest who may or may not. It's a logical fallacy. That doesn't prove you're wrong, but you haven't really demonstrated anything either.

pj
chgo